              m att
              :when (and (not (inz [g m]))
                         (forall [n att]
-                          (=> (proper-subset? (prime m) (prime n))
-                              (inz [g n]))))])))
+                          (or (inz [g n])
+                              (not (proper-subset? (prime m) (prime n))))))])))
 
 (defn up-down-arrows
   "Returns up-down-arrow relation of ctx."

             m atts
             :when (and (not (inz [g m]))
                        (forall [h objs]
                          (=> (proper-subset? (oprime g) (oprime h))
                              (inz [h m])))
                        (forall [n atts]
                          (=> (proper-subset? (aprime m) (aprime n))
                              (inz [g n]))))])))

(defn reduce-objects
  "Object reduction for ctx."

             m att
             :when (and (not (inz [g m]))
                        (forall [h obj]
                          (or (inz [h m])
                              (not (proper-subset? (prime g) (prime h))))))])))

(defn up-arrows
  "Computes the up arrow relation of ctx."
